Article Goal

• Learn to import and export YCoCg UI images
• tip You don’t need to remember technical details about YCoCg images, just be aware conversion is happening in the background.

YCoCg Images

While most icons use standard DDS image resources, images in UI.package typically use a special format called YCoCg. This includes many UI components and all world map backgrounds.

YCoCg images don’t use RGB color space, but instead use YCoCg color space. Additionally, the image data is stored in two separate resources instead of just one. S4E allows you to view the combined image.

If you search the instance in the All Resources tab, you’ll see the two YCoCg parts. The combined image isn’t saved as a resource, it is generated as needed by both Sims 4 and S4E.

If you do care about technical details, you can learn more about YCoCg in the Images Article.

Exporting

Sims 4 Editor lets you export combined UI images as .png images.

1. S4E Homepage > Game File Browser > UI Images
2. Select an image, right click to export
   • When exporting maps, you can select Crop Map Images, explained further down.

Blurriness

One of the YCoCg parts is stored at half resolution, so images are slightly blurry when exported. It isn’t too bad with small images, but gets more noticeable with larger images.

Importing

To have Sims 4 Editor import an image as YCoCg, add .ui before the image extension. For example: Willow Creek-0x22FE7C4C083A3FBA.ui.png. This will cause S4E to split the image into two YCoCg resources.

Map Overrides

When importing map images, use .map instead of .ui, making the more correct example Willow Creek-0x22FE7C4C083A3FBA.map.png. This will check the image size and uncrop if necessary.

Resolution

Because maps are heavily affected by the upscaling issue, you typically only want to use exported maps as a template, scale them to 2x the size, then create your new map using high resolution assets.

Cropping

Maps have a giant empty space in the bottom right because they are cropped by the game. S4E can automatically crop and uncrop map images to make them easier to work with.

When importing, using .map before the image extension causes S4E to make sure the image is one of the four valid sizes, and uncrops it if required. The valid sizes:

	Cropped	Uncropped
Standard	1536x1080	2048x2048
HD (2x)	3072x2160	4096x4096

Example Mod

Willow Creek Map Replacements

This mod replaces the Willow Creek map with a space background from Pixabay. There are 2K and 4K versions to show the difference in quality.

• ZMilla-WillowCreekSpace-2k.package
• ZMilla-WillowCreekSpace-4k.package